1. Field of the Invention
The present invention relates to an X-ray detecting device and a driving method thereof. More particularly, the present invention relates to an X-ray detecting device for increasing detection efficiency by controlling capacitance of an integrator according to transmissivity of a subject, and a driving method thereof.
2. Description of the Related Art
An X-ray detecting device detects an X-ray image of a subject taken by an X-ray generating device and provides the image to a display device. An X-ray detecting device of the flat panel type using digital radiography using no film has been generally used. The flat panel X-ray detecting device includes a plurality of photodetecting pixels for detecting the X-rays on the flat panel. Each photodetecting pixel detects the X-rays generated by the X-ray generating device and outputs electrical signals. The electrical signals are read out from the flat panel by a readout integrating circuit (ROIC) for respective rows. The signals output by the readout integrated circuit are processed to be converted into video signals to be transmitted to the display device for displaying the X-ray image.
Performance of the X-ray detecting device is expressed by the detective quantum efficiency (DQE), and when increasing the detective quantum efficiency of the X-ray detecting device, it is a good method for the X-ray generating device to irradiate X-rays with high intensity of radiation or minimize a load of a data line on the flat panel and increase photosensitivity of a PIN diode. A method for increasing the detective quantum efficiency of the X-ray detecting device is proposed as the automatic exposure control (AEC) method. The AEC method represents a load condition control method for the X-ray generating device to automatically control the intensity of radiation irradiated on predetermined various subjects.
Also, the detective quantum efficiency of the X-ray detecting device is influenced by a performance gain of a readout integrated circuit (ROIC) for reading out the electrical signals. Generally, the readout integrated circuit includes a feedback capacitor having constant electric capacity considering entire transmissivity of the subject. For example, when an X-ray image of a person is taken, transmissivity is variable by the body shape and parts of which the image is taken. In consideration of this point, the conventional X-ray detecting device uses a feedback capacitor having constant electrical capacity that is applicable irrespective of the targets of which the image is to be taken.
It takes 1 to 2 seconds for the conventional X-ray detecting device to detect the subject's X-ray image and read it. However, an X-ray detecting device for detecting and reading a taken image at a high speed is required, and the existing device using a feedback capacitor with constant electrical capacity is inappropriate for high-speed operation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.